Manufacture of styphnic acid salts



Patented Mar. 3, 1942 MANUFACTURE OF STYPHNIC ACID SALTS Willi Briin,Bridgeport, 001111., assignor to Remington Arms Company, Inc., acorporation of Delaware No Drawing. Application November 28, 1940,Serial No. 367,609

2 Claims. (01. 260-435) This invention relates to the manufacture ofstyphnic acid and certain of its salts, and contemplates improvementsand refinements in the production of styphnic acid, the practice ofwhich results in a product adapted to be made into salts having certaindesirable properties and characteristics.

The present application is a continuation in part of my prior co-pendingapplication, Serial No 207,784, filed May 13, 1938, which is a divisionof application Serial No. 674,049, filed June 2, 1933, now Patent No.2,137,234, November 22, 1938.

More specifically, the invention contemplates the control of the shapeand form of the crystals of certain salts of styphnic acid, particularlybasic lead styphnate, and certain methods in the manufacture of styphnicacid which enable the acid to form salts having novel and desirablecrystal shapes. r

The manufacture of basic lead styphnate, and particularly a redcrystalline form thereof is described in this applicants Patent No.1,942,274, January 2, 1934. It may be briefly summarized as follows: Asolution of styphnic acid and sodium hydroxide, in the proportions of12.2 grams of styphnic acid and 8 grams of sodium hydroxide in 400 c. c.of water, is dropped into a lead nitrate solution of the concentrationof about 35 grams of lead nitrate in 350 c. c. of water. The temperatureis maintained between 60' and 70 C., and the styphnic acid-sodiumhydroxide solution is at first dropped into the lead nitrate solutionvery slowly. The first precipitate is a previously known yellowamorphous or partly amorphous basic lead styphnate which, if the sodiumhydroxide-styphnic acid solution is at first introduced quite slowly,changes over to a heavier red crystalline basic lead styphnate whichquickly settles out.

When in the practice of the process above outlined ordinary styphnicacid is used, the crystals of basic lead styphnate are rather thickhexagonal plates. They are less fragile and sensitive to friction andshock than the previously known yellow needle crystals. The presentinvention comprises the discovery of other crystalline forms of basiclead styphnate, and methods for producing basic lead styphnate in theseforms. The novel crystal shapes result from the use of styphnic acidmade in accordanc with certain procedures constituting a part of thepresent invention. The manufacture of ordinary styphnic acid will firstbe briefly described:

The raw material is resorcine (CeH4(OI-I)2).

. of a number of different substances.

By treatment with concentrated sulphuric acid, resorcine is sulphonatedto resorcine-di-sulphonic acid, CeH2(OH)2(SO3H)2. Theresorcine-di-sulphonic acid is then nitrated with concentrated nitricacid. The precipitated styphnic acid is separated from the residue bycentrifugal action or by filtration, and subsequently Washed, first witha dilute mineral acid and then with water. If the sulphonation of theresorcine is complete, the resulting product is .pure styphnic acid of abright yellow color and low gravimetric density, from which crystallinesalts are formed only with great difficulty.

The present invention comprises the discovery that the character of thestyphnic acid may be altered in such a way as to control the crystalshape of the salts which it forms by the addition, during the operationof sulphonating, of small amounts of certain foreign substances. Suchvariations in the styphnic acid and in the crystal shape of its salts,particularly the basic lead salt, are produced by the use of any oneMoreover, each substance has the property of producing its owncharacteristic effects and crystal shape, each of these shapes differingfrom the others. For example, if to a batch comprising grams ofresorcine and 460 c. c. of 98% sulphuric acid there be added 10 c. c. ofconcentrated nitric acid, the resulting styphnic acid is darker in colorand less voluminous and itssalts have different physical properties. Thefurther addition of .1 gram of tri-oxy-methylene results in a styphnicacid which yields its basic lead salt in crystals of a shape differingvery substantially from the usual crystals of this salt. Said crystalsare somewhat elongated-square or rectangular prisms, as distinguishedfrom the usual hexagonal plates, and appear to be more sensitive toshock and friction than the hexagonal plates. Two opposite faces of therectangular prismatic crystals appear to be substantially square, whilethe other faces are rectangles having a length of the general order ofthree or four times their Width.

The use of catechol in place of tri-oxy-methylene produces a styphnicacid whos basic lead salt likewise forms in square prismatic crystals,but these crystals are much shorter (more nearly cubical) than thoseresulting from tri-oxymethylene. The procedure is as follows: Thecrystal controlling agent is preferably introduced into the sulphonatingsulphuric acid. Just as with tri-oxy-methylene, improved results aresecured if a small amount of nitric acid is also used. In 460 c. c. of98% sulphuric acid there is mixed 10 c. c. of concentrated nitric acidand .5 gram of crystalline catechol. The acid thus prepared is pouredover 110 grams of resorcine, this being the usual procedure in thesulphonation of resorcine. The manufacture of styphnic acid and thesalts thereof, such as the basic lead styphnate, is then completed inthe manner heretofore described.

The use of glucose in place of tri-oxy-met'nylene or catechol as abovedescribed produces greatly elongated rectangular crystals of the salts.For this purpose, crystalline glucose is used in exactly the same manneras tri-oxymethylene or catechol, .25 gram thereof being a desirablequantity for additional to 460 c. c. of 98% sulphuric acid and 10 c. c.of concentrated nitric acid, the mixture being used in the sulphonationof 110 grams of resorcine.

The use of phenol in place of any of the addition agents above-mentionedlikewise produces a characteristic crystal, differing from that producedby any of the other addition agents. These crystals are substantiallyrectangular in cross section and extremely long. A desirable quantity is1 gram of crystalline phenol with 10 c. c. of concentrated nitric acidin 460 c. c. of 98% sulphuric acid, the mixture sulphonating 110 gramsof resorcine.

The use of aluminum in the same manner produces crystals which are verynearly cubical and exceptionally clean. 1 gram of powder of aluminum and10 c. c. of concentrated nitric acid are added to 460 c. c. of 98%sulphuric acid, which is then used for the sulphonation of 110 grams ofresorcine.

The use of glacial acetic acid as an addition agent produces a strikingeffect in that the salt crystals are short, rectangular prisms withrounded corners, somewhat resembling the crystals of normal leadstyphnate. Such crystals are produced from styphnic acid, in thepreparation of which about 5 c. c. of glacial acetic acid and c. c. ofconcentrated nitric acid have been added to 460 c. c. of 98% sulphuricacid, which is then used for the sulphonation of 110 grams of resorcine.

The use of water as an addition agent produces a salt in crystals whichare nearly cubical and exceptionally firm and dense. Such crystals areproduced from styphnic acid in the preparation of which about c. c. ofwater and 10 c. c. of concentrated nitric acid are added to 460 c. c. of98% sulphuric acid, which is then used for the sulphonation of grams ofresorcine.

It should be remembered that the foreign substance is introduced in thesulphonation operation in the preparation of styphnic acid, and that thedescribed crystal shapes are those of the salts, particularly the basiclead salt, of the acid produced by the nitration of resorcine disulphonic acid made in the presence of the foreign substance.

No satisfactory theoretical explanation of these effects can be offered.The foreign substances which cause them do not fall within anyrecognized class, or appear to have any property in common other thantheir ability to change the crystal shape of basic lead styphnate fromhexagonal to generally rectangular. Limited oxidation of the resorcineor the resorcine-di-sulphonic acid may be a factor, but oxidation alonecannot account for effects which are individual to the differentaddition agents.

What is claimed is:

1. In the manufacture of a lead salt of styph nic acid by thesulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the step whichcomprises the addition of aluminum to the sulphonating acid, whereby ina subsequent step said lead salt is formed in crystals of aconfiguration characteristic to said addition.

2. In the manufacture of basic lead styphnate by a process including thesulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the step whichcomprises the addition of aluminum to the sulphonating acid, whereby ina subsequent step said basic lead styphnate is formed in crystals of aconfiguration characteristic to said addition.

WILLI BRI'jN.

